The prior art golf clubs and shafts thereof have a degree of flexibility that is greatly dependent on the shaft material. Each individual golfer, especially a skilled player, has a preference for certain characteristics, such as feel, in a golf club or set of clubs. Generally feel is measured by the flexibility of the golf club shaft. One golfer may prefer a stiff feel, while others may prefer a more flexible club. Flexibility of golf club shafts can even vary from one section of the shaft to another, such as in the tip, butt, and intermediate sections.
U.S. Pat. No. 5,620,380 to Tennent et al. relates to a light weight golf club shaft described as having a “modified hourglass” shape which provides many predetermined combinations of flex, stiffness and torque which together are perceived as shaft and club “feel.” The shaft reportedly reduces shaft weight to the level desired by a golfer by using a substantially uniform shaft wall thickness while maintaining the unique “hour glass” external profile of our previous shaft. The shaft is formed of a base with axial sections: a grip section, an upper flare section, a flex control section, a lower flare section, and a hosel section, the whole forming an exterior shaft profile. The shaft may be made from metal such as steel, titanium, aluminum or their alloys, or composites formed of reinforcing fibers and polymeric materials. The preferred fibers for reinforcement are the carbon, ceramic, metallic, glass, aramid and extended chain polyethylene fibers, most preferably the carbon fibers. Preferred among the polymers which may be used are thermosetting resins such as the phenolics, polyesters, melamines, epoxies, polyimides, polyurethanes and silicones. The shafts reportedly may be produced by a variety of methods, including casting, molding (as around one or more mandrels), expanding or drawing.
U.S. Pat. No. 6,071,460 to Renaudin et al. relates to an apparatus for manufacturing a reinforced golf club shaft having a complex shape. An inflatable bladder is positioned over a mandrel having a simple shape. Layers of fiber material are then rolled over inflatable bladder to produce a sub-assembly. The sub-assembly is placed in a mold defining a negative of the shape of the final shaft that is to be produced. The impression may have enlarged or narrowed regions for producing irregularities in the shape of the shaft. The bladder is expanded within the mold so that the composite structure is radially displaced and compressed between the bladder and the mold. The inflatable bladder has a variable thickness that conforms to the shape of the impression so that the composite structure undergoes a uniform and minimum displacement along its entire length, which reportedly improves the mechanical properties of the final shaft.
U.S. Patent Application Publication No. 2001/0014626 to Takiguchi et al. relates to a golf club shaft and a method especially suited for producing the shaft that reportedly provides high rigidity and ease of use and that allows inexpensive and easy manufacture. A sloped section 16 expanding toward a grip end 14 is formed. The sloped section has a slope gradient of 15/1000-35/1000 and a length of 200-350 mm. The outer diameter of the grip end is 18-25 mm. On the side of the sloped section toward an end 18, there is formed a semi-sloped section 19 with a slope gradient of 4/1000-13/1000. A kick point is formed at a position 40-46% from the small-diameter end relative to the shaft length.
The prior art golf club shafts and processes for making the same have been limited in design and functionality by their production devices. The golf club shafts of the present invention overcome the aforementioned problems.